~9. How to Breathe.~--We should always take pains to expand the lungs
well in breathing, and to use the entire chest, both the upper and the
lower part. Clothing should be worn in such a way that every portion of
the chest can be expanded. For this reason it is very wrong to wear the
clothing tight about the waist. Clothing so worn is likely to cause the
lungs to become diseased.

~10. Bad Habits.~--Students are very apt to make themselves flat-chested
and round-shouldered by leaning over their desks while writing or
studying. This is very harmful. We should always use great care to sit
erect and to draw the shoulders well back. Then, if we take pains to
fill the lungs well a great many times every day, we shall form the
habit of expanding the lungs, and shall breathe deeper, even when we are
not thinking about doing so.

~11. Breathing through the Nose.~--In breathing, we should always take
care to draw the air in through the nose, and not through the mouth. The
nose acts as a strainer, to remove particles of dust which might do harm
if allowed to enter the lungs. It also warms and moistens the air in
cold weather. The habit of breathing through the mouth often gives rise
to serious disease of the throat and lungs.

~12. Effects of Alcohol and Tobacco upon the Lungs.~--Both alcohol and
tobacco produce disease of the breathing organs. Smoking injures the
throat and sometimes causes loss of smell. Serious and even fatal
diseases of the lungs are often caused by alcohol.

~13.~ Many people suppose that the use of alcohol will save a man from
consumption. This is not true. A man may become a drunkard by the use of